.\" Copyright (c) 2008 Konstantin Belousov
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.\" $FreeBSD: head/share/man/man9/dev_clone.9 186714 2009-01-03 10:37:38Z brueffer $
.\"
.Dd January 3, 2009
.Dt DEV_CLONE 9
.Os
.Sh NAME
.Nm dev_clone ,
.Nm drain_dev_clone_events
.Nd eventhandler for name-based device cloning in devfs
.Sh SYNOPSIS
.In sys/param.h
.In sys/conf.h
.Ft void
.Fn clone_handler "void *arg" "struct ucred *cr" "char *name" "int namelen" "struct cdev **dev"
.Bd -literal
EVENTHANDLER_REGISTER(dev_clone, clone_handler, arg, priority);
.Ed
.Ft void
.Fn drain_dev_clone_events
.Sh DESCRIPTION
A device driver may register a listener that will be notified each time
a name lookup on the
.Xr devfs 5
mount point fails to find the vnode.
A listener shall be registered for the
.Va dev_clone
event.
When called, it is supplied with the first argument
.Va arg
that was specified at handler registration time,
appropriate credentials
.Va cr ,
and a name
.Va name
of length
.Va namelen
that we look for.
If the handler decides that the name is appropriate and wants to create the device
that will be associated with the name, it should return it to devfs
in the
.Va dev
argument.
.Pp
The
.Fn drain_dev_clone_events
function is a barrier.
It is guaranteed that all calls to eventhandlers for
.Nm dev_clone
that were started before
.Fn drain_dev_clone_events
call, are finished before it returns control.
.Sh SEE ALSO
.Xr devfs 5 ,
.Xr namei 9